Wheel Hub queries

I have recently obtained replacement wheel hubs for a S2, I wanted the larger stud type as used on early S3's, I obviously need to drill the brake drum holes out to facilitate the larger studs, anyone experienced problems doing this?
During the same 'project' I aim to fit a couple of manual AVM freewheel hubs that i obtained a year or more ago - anyone got ANY servicing/overhaul info on these things. AVM in Brasil are of no help whatsoever and neither are any European agents.

The stud size changed about 1967 so late 2As also have the larger studs,just fit new drums.